Enlarge / People may accidentally sequence your DNA while trying to study something else entirely. (credit: Andriy Onufriyenko )

It used to be that if you wanted to find a DNA sequence in a particular sample, you had to go searching for that specific sequence—you had to fish it out with a hook designed especially to catch it. But no more. DNA sequencing technology has advanced to the point where you can take a sample from almost any environment—a drop of water, an ice core, a scoop of sand or soil, even air—and just see whatever DNA is in there.

This provides a non-invasive way to study wild populations and invasive or endangered species and has been used to monitor for pathogens (SARS-CoV-2, mpox, polio, tuberculosis) in wastewater. But guess who else’s DNA is in those environmental samples? Yup. Ours.

Something identifiable in the air

Liam Whitmore is a zoologist and conservationist who studies green turtles. He and his colleagues realized that having human DNA slip into research samples might be an issue, so they looked to see if they could find any in old water and sand samples they had taken as part of a wildlife and pathogen monitoring study. They did. Then they went intentionally searching for specific human sequences, and, in water, sand, and air samples, they found plenty of genomic regions that could identify a person’s ancestry and susceptibility to several diseases. They didn’t go so far as to identify individuals but noted that someone probably could compare these sequences to public genetic data without too much difficulty.

Enlarge (credit: The Burtons )

The business sector has had a fraught relationship with conservation. While many companies are now pushing to make their products and operations less damaging to the environment, the private sector, broadly speaking, has made life harder for the world’s complex ecosystems and the organisms in them.

For those companies looking to understand their environmental impacts better, NatureMetrics, a UK-based company, recently launched a service that can potentially inform conservation efforts in the private sector. The company is in the early stages of launching a subscription service that lets corporations regularly check their sites for biodiversity and keep an eye on any changes—good or bad—their activities have.

“You need to be doing monitoring over time in a structured way with enough samples to give you statistical significance,” Katie Critchlow, NatureMetrics’ CEO, told Ars.

Enlarge / An attempt to reconstruct what northern Greenland looked like about 2 million years ago. (credit: Beth Zaiken )

When once-living tissue is preserved in a cold, dry environment, fragments of its DNA can survive for hundreds of thousands of years. In fact, DNA doesn't even have to remain in tissue; we've managed to obtain DNA from the soil of previously inhabited environments. The DNA is damaged and broken into small fragments, but it's sufficient to allow DNA sequencing, telling us about the species that once lived there.

In an astonishing demonstration of how well this can work, researchers have obtained DNA from deposits that preserved in Greenland for roughly 2 million years. The deposits, however, date from a relatively warm period in Greenland's past and reveal the presence of an entire ecosystem that once inhabited the country's north coast.

A different Greenland

Over the last million years or so, the Earth's glacial cycles have had relatively short warm periods that don't reach temperatures sufficient to eliminate the major ice sheets in polar regions. But before this time, the cycles were shorter, the warm periods longer, and there were times the ice sheets underwent major retreats. Estimates are that, around this time, the minimum temperatures in northern Greenland were roughly 10° C higher than they are now.